PANNA: Swedish Study Shows Power of Prevention

A recent study in Sweden provides concrete evidence that preventative public health measures produce healthier populations. The study, which analyzes data from the National Swedish Cancer Registry, links Sweden's national policies to reduce chemical exposure with fewer cases of non-Hodgkin's lymphoma (NHL).

The Cancer Registry data indicate the incidence of NHL increased annually in Sweden at a rate of 3.2% for men and 3.1 % for women between 1971 and 1990. The increase became a decrease (0.8% for men and 0.2% for women) between 1991 and 2000, roughly 20 years after use of a number of chemicals associated with NHL was severely restricted. Similar trends have been noted in Finland, Denmark and the U.S.

Dr. Ted Schettler, of the Science and Environmental Health Network said of the study, "If this is true, it's good news because it shows that yet another cancer can be prevented by reducing exposures to cancer-causing chemicals, rather than having to focus almost exclusively on cures pursued for decades by the health establishment."

NHL is associated with a decrease in immune system function and has been connected with exposure to three types of chemicals: phenoxyacetic acids and chlorophenols; organic solvents; and persistent organic pollutants. The HIV virus has also been shown to be a risk factor for NHL. Since the cancer can develop decades after exposure, an emerging trend in NHL now is likely to be the result of environmental factors decades ago.

The Swedish researchers developed a mathematical model to arrive at a percentage of NHL cases that could be attributed to exposure to a specific chemical, based on risk estimates and exposure frequencies found in their previous case studies. With this method they calculated, for example, that 25% of Swedish NHL cases could be attributed to organic solvent exposure.

Chlorophenoxyacetic acids (used in the herbicide Hormoslyr) and chlorophenols (used primarily as impregnating agents for wood preservation and as microbiocides) were both banned in Sweden during the 1970's. Organic solvents were not banned, but occupational exposures were reduced by stricter handling instructions. Restrictions on the use of these chemicals, improved work practices to reduce occupational exposure, and cleaner products may all have contributed to the lower rates of NHL in Sweden.

Other chemicals linked to NHL are persistent organic pollutants such as organochlorine pesticides (e.g., DDT, chlordane, hexachlorobenzene) polychlorinated biphenyls (PCBs), and dioxins. All of these chemicals are among the 12 slated for global elimination under the 2001 Stockholm Convention (see August 29th PANUPs for an update on the current status of the treaty). Exposure to these persistent chemicals is widespread, and occurs primarily through the food chain. A study done by the US National Cancer Institute and the US Centers for Disease Control indicates that exposure to PCBs, when combined with the Epstein-Barr Virus (EBV) antigen, greatly increases the risk of NHL. The Swedish Environmental Protection Agency reports that the use of these chemicals peaked during the 1960's and 1970's, after which concentrations of PCBs dropped significantly in the environment and the food chain.

The Surveillance Epidemiology and End Results (SEER) indicates that trends in the United States are similar to Sweden. Between 1973 and 1990 the incidence of NHL increased by 3.6% per year. Between 1990 and 1995 the increase was only 1.6% per year, and between 1995 and 1999 NHL incidence declined by 0.9% for men only, while women experienced a lower mortality rate. Significantly, the lowered incidence of NHL in the U.S. also occurred approximately 20 years after most uses of the chlorophenoxy herbicide 2,4,5-T were banned.

A May 2003 report by the Physicians for Social Responsibility (PSR) recognized NHL as the fifth most common cancer in the United States, and pointed to dramatic increases in cases of NHL between 1947 and 1990, when rates rose by more than half for men and women between 25 and 44, doubled for those 44 to 65, and tripled for 65 and older. The study also notes links between farming and higher rates of NHL. The PSR report called for better tracking of location and occupation in cancer statistics, to address the connection between chronic disease and the environment.

Although the model used in this study may need more evaluation and study, this work clearly shows that preventative policy measures can result in a clear public health benefit. The results also lend urgency to worldwide ratification of the Stockholm Convention.

PANUPS is a weekly email news service providing resource guides and reporting on pesticide issues that don't always get coverage by the mainstream media. It's produced by Pesticide Action Network North America, a non-profit and non-governmental organization working to advance sustainable alternatives to pesticides worldwide.

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